Create the pd.ExcelFile() object using the file listings.xlsx and assign to the variable xls.
Retrieve the sheet names from the .sheet_names attribute of xls and assign to exchanges.
Create an empty list and assign to the variable listings.
Iterate over exchanges using a for loop with exchange as iterator variable. In each iteration:
- Use pd.read_excel() with xls as the the data source, exchange as the sheet_name argument, and 'n/a' as na_values to address missing values. Assign the result to listing.
- Create a new column in listing called 'Exchange' with the value exchange (the iterator variable).
- Append the resulting listing DataFrame to listings.
Use pd.concat() to concatenate the contents of listings and assign to listing_data.
Inspect the contents of listing_data using .info().

Reading, inspecting, and cleaning data from CSV